Scrub Oak Bulging Base & Bark Separation: Borer Damage

100+ scrub oaks N. of Sacramento; one has bulging base (18″), bark separating/crumbing.

Diagnosis: Borers

Bark separation + frass = borer larvae feeding under bark.

Treatment

1. Spray trunk with Onyx or Merit (penetrate bark, kill larvae).
2. Fertilize: 1 lb 10-10-10 per inch DBH — borers attack stressed trees.
3. Apply now & spring.

Check garden center for products. Monitor others for early signs.